The invention concerns a sealing device for sealing container bowls with a heat sealing film, the sealing device comprising several container receptacles for simultaneous receiving of several container bowls as well as several sealing heads associated each with a container receptacle, wherein the several sealing heads for simultaneous sealing of the heat sealing film onto the several container bowls are movable in a sealing stroke direction relative to the container receptacles, wherein the several container receptacles are fixedly connected to each other and in particular combined in a common receiving block, and wherein the several sealing heads in a rest position are forced with pretension by means of a spring element, respectively, in the sealing stroke direction against a stop, each sealing head having one stop associated therewith. The invention further relates to an associated method for sealing such container bowls with a heat sealing film.
In various application situations, products are stored in sealed containers. According to the prior art, the corresponding packaging process is realized in that individual container bowls are provided and filled with the respective product. Several such individual and filled container bowls are then subsequently and simultaneously sealed with a continuous heat sealing film so that a continuous strip of containers is produced. Only at a later point in time the container strips are individualized to individual sealed containers. In the known embodiments, the several container bowls are arranged in the form of a matrix. With application of pressure and temperature, a common sealing head that covers the entire matrix is then lowered, with intermediate positioning of the heat sealing film, onto the filled container bowls that are received in container receptacles. A problem in this context is that the individual container bowls have thickness tolerances and position tolerances which cannot be compensated by the sealing head that is jointly acting onto the several container bowls. As a result, there is the risk that individual container bowls and the heat sealing film resting thereon are not subjected to a uniform and satisfactory sealing pressure or that individual container rims that are too thick are excessively melted under pressure that is too high and are thereby deformed too much. The sealing action can therefore be defective and can lead to undesirable rejects.
EP 1 545 977 B1 and EP 1 013 548 B1 are dealing with the aforementioned problem, wherein in various embodiments the same basic principle of tolerance compensation is employed. The individual container bowls that are to be sealed simultaneously are held individualized in their own correlated container receptacles wherein these individual container receptacles are moveable independently of each other and relative to each other in a yielding fashion. A plunger with a large sealing head that covers several container bottom parts or even individual plungers with a single sealing head each associated with a single container bottom part are then moved, in particular pneumatically, against the container bottom parts so that a sealing process takes place. The pneumatic pressure for movement is controlled so that, in connection with the individual yielding suspension of the individual container bottom parts, a uniform sealing pressure with tolerance compensation is supposed to be realized.
A problem here is the high expenditure for the device and the control circuit. The individual suspension of the container bottom part is complex and cost-intensive wherein an exact adjustment of the controlled contact pressure is required.
The invention has the object to further develop a sealing device of the aforementioned kind in such a way that with simplified construction and increased processing reliability a reliable sealing action with tolerance compensation can be performed.